1. Field of the Invention
This invention relates to a process for forming light-sensitive silver halide crystals and, more particularly, to a process for growing crystal grains of light-sensitive silver halide.
2. Description of the Prior Art
Most of the emulsions in presently commercially available high speed photographic films are polydisperse emulsions containing multiple twin crystal grains. A narrow grain size distribution of the grains often serves to improve many photographic properties. For example, graininess is improved, and the emulsion becomes contrasty. However, there have so far been no techniques to remarkably narrow the grain size distribution of multiple twin crystal grains. According to British Pat. No. 1,520,976, an emulsion containing multiple twin crystal grains having a mean grain size of 0.93 .mu.m with a variation coefficient of 20% is prepared by forming grains containing 90 mol % or more silver iodide at the initial stage of the formation of precipitates. However, this process is restricted to the formation of twin crystal grains by initiating the grain formation with grains containing 90 mol % or more iodide, and the grain size distribution of the resulting grains is not said to be sufficiently narrow.